Hi Josh, welcome to the forum.
Sounds like your power supply is working, which is the good news.
I know you checked your wiring three times, but check again. Make sure the middle lug of the P1 pot is connected to B+3. That's where the 1K2 and 22k resistors connect. Also
meilleurs credits perso make sure the other two lugs connect to the 100K and 110K resistors. And make sure there are no accidental shorts in this area, or anywhere else on the board, or when the board got mounted to the chassis. Check for shorts at the tube sockets, too. Sometimes a stray bit of wire or solder is hard to see.
Also make sure the value of the pot was correct. The layout drawing says it's 5K. The schematic doesn't say what it is.
Were all the tubes in place when the pot fried?
I’m leery to measure pins directly because of proximity to the other lugs.